Apparatus for nibbling



pt. 1, 1953 G. F. WALES ET AL 2,650,663

I APPARATUS FOR NIBBLING Filed Dec. 29, 1948 3 Sheets-Sheet l a AMA A A'I/ A l rl lbx/ 1 lf w y fig .INVENT G. F. WALES ET AL 2,650,663

APPARATUS FOR NIBBLING' Sept. 1, 1953 Filed Dec. 29. 1948 3 Sheets-Sheet2 l HHII Sept. 1, 1953 G. F. WALES ET AL APPARATUS FOR NIBBLING FiledDec. 29. 1948 3 Sheets-Sheet 5 Patented Sept. 1, 1953 UNITED STATESATENT ()FFICE APPARATUS FOR NIBBLING George F. Wales, Kenmore, and PaulH. Taylor, North Tonawanda, N. Y.; said Taylor assignor to said Wales 13Claims. 1

This invention relates to perforating apparatus and more particularly isconcerned with novel methods and apparatus for cutting sheet material bynibbling.

There are several methods of cutting the contoured sheet metalwork-pieces which are used in .industry for the production of consumergoods.

For high production runs a male and female die are generally employedwhich blank out the work-piece in one, two or more operations, dependingupon its character. This is the method of tooling employed in all highproduction industries. However, a large majority of applications aresuch that this expensive form of tooling would not be justified by theprobable production runs to be made. For instance; in medium rangeproduction it is a general practice to overcome the high cost of theabove finished dies by making temporary dies to provide a work-piece.These temporary dies have a short life and provide a work-piece whichgenerally requires finishing operations. Because of tooling costs, inlow production work it has been the general practice to saw, use handsnips, or any other type. of hand tool to provide the approximate,work-piece and then complete the work of finishing the edge of thework-piece by filing or other hand operations. In recent years apractice has developed of nibbling the low and some medium productionrun work-pieces because the greater rapidity of the perforationoperation made this; process more economical than some dies and the handopera tions. However, because the nibbling operation is generally donewith a round punch, an unfinished edge is always obtained if the maximumfeed of nibbling is undertaken. That is, if the feed of the nibblingoperation is rapid the circular shape of the punch leaves a scallopededge along the work-piece which must be dressed or? if a finished edgeis: required. This condition can. be alleviated somewhat by slowing thefeed of the work-piece so that a very fine scalloped edge is developed,which is satisfactory in many cases without further operation. It willbe obvious though, that if the speed of operation is slow, theadvantages of nibbling are largely st and sawing or some other method ofpreparing the work-piece might just as well be utilized, unless thescalloped edge of the high feed condi tion can. be hidden from the eye.Because of the above difficulties many companies have abandoned the useof nibbled work-piecesv for any parts which appear to the customers eye.Due to the low cost of nibbling, however, these companies havecontinued: to utilize nibbled parts where they are hidden from thecustomers view, so that the scalloped edge was not objectionable. Inaddition, some companies have utilized an oblong or rectangular punchfor nibbling along a straight line or for round ends exposed to the eyeof the consumer as the series of flats on the straight line or peripheryof the nibbled blank generally proved satisfactory without furtherfinishing or other rework.

It will now be obvious to those skilled in the art, that where thescalloped edge of a contoured work-piece can be hidden or where a flatpunch for a straight line or a fixed radius can be employed, the presentpractice of nibbling can be utilized. However, it will be readilyapparent that this excludes nibbling a large share of the low and mediumproduction run work because it employs varying contours and is visibleto the eye.

Another difficulty experienced with the high rate of perforationsencountered in nibbling, was the necessity for removing the punch anddie more often for sharpening or replacement. The excessive time lost inreplacing punches and dies raised the cost of nibbling. To overcome thislost time we devised a self-contained nibbling unit similar to thequick-change perforating unit which is illustrated in Fig. 15 of PatentNo. 2,364,- 011. This patent is a modification of basic Patent 1,955,866and both of these patents are assigned to our interests. However, thehigh perforating rate when nibbling made more critical a difficultyexperienced in this construction due to the rapid dulling of punch anddie. Since a dull punch and die greatly increases the stripping forcerequired over that for a sharp punch and die, the variation in strippingpressure changes rapidly when nibbling, due to the rapid dulling of thepunch and die. The continuous reciproeating operation is at the rate ofto 800 strokes per minute and this prevents discovering a dull punch atthe instant it. fails to strip so that damage may result as will bedescribed hereinafter. In single perforating work the ram stops at theend of each perforation and a dull punch can be detected because thestripping spring fails to withdraw the punch from the work-piece. Thepunch can then be removed and replaced or sharpened without causingdamage.

When a punch ticks in nibbling it may withdraw suddenly from thework-piece at the in.- stant the ram is at the top of its strokeallowing the punch to strike the ram sufficiently hard. to damage thepunch or ram. In the event the self containednibbling device is beingused: on a long stroke press-working machine, the gap between the headof the punch and the ram, in its upper position, may be suflicient toallow the punch to jump completely out of the holder and the succeedingstroke of the ram may cause great damage and create hazard to themachine operator. While a heavier spring may be utilized, stickiness maystill occur and the stored inertia in the heavier spring may make itwithdraw more severely driving the punch out of the holder. In addition,the heavier spring is generally more subject to fatigue and raises theperforating load on the machine. Although methods for restraining thesprings under initial tension have proven moderately successful onsingle hole units, the continuous operation of the nibbling cycleprevents the use of restraining means for nibbling punches.

The primary object of our invention is to provide a companion nibblingpunch and die which will provide a finished edge regardless of thecontour around which they are travelling.

Another object of our invention is to provide a nibbling punch and diewhich provides a finished edge and yet permits maximum machine toolspeed.

A companion object of our invention is to provide a companion nibblingpunch and die which are easily manufactured.

Yet another object of our invention is to provide a nibble punch and diein which the component most easily replaced is provided with thevariable clearances for various material thicknesses.

Yet a. further object of our invention is to provide a companion punchand. die for nibbling which is adapted to nibble around a work-piece onfixed centers or around a template.

Still a further object of this invention is to provide a companionnibbling punch and die adapted to be installed in a self-containedholder assembly.

A related object of this invention is to provide resilient biasingmeans, for stripping the punch from the work-piece, which matches thestripping force required at any material thickness.

Still another related object of this invention is to reduce the dynamicenergy after stripping.

Still another object of this invention is to provide novel key means formaintaining a shaped punch and die in alignment.

Still a further object of this invention is to provide novel key meansfor maintaining the punch and die in aligned relationship.

Another object of this invention is to provide a novel nibblingapparatus and method in which the punch and die turn in relation to thedesired feed rather than the work-piece.

A related object of this invention is to provide novel apparatus andmethods for nibbling around templates, to fixed gauges and to a scribedline.

Fig. 1 is a side elevation showing our punch and die as adapted to aself-contained holder such as shown in Patents Nos. 1,955,866 and2,364,011 and illustrating a method of nibbling a work-piece from ajuxtaposed template.

Fig. 2 is a sectional view taken in line 22 of Fig. 1, showing therelative relation of the punch, its adjustable head, nested strippingsprings, stripping guide and die of our device, and illustrating the keypin extended through the stripping guide for guiding the punch and diewith relation to the holder for the novel method of nibbling to fixedgauges or centers.

Fig. 3 is a perspective view of our punch illus- 4 trating the keyedsection for keying the punch to the die and the adjacent nibblingcutting surfaces of said punch.

Fig. 4 is a sectional view taken as noted of Fig. 2, showing thehalf-round punch section and the notched guide sleeve which permits thetemplate to be in juxtapposition to the flat punch surface.

Fig. 5 is a section on the line 55 of Fig. 2, showing a section of thedie, which illustrates the slug clearance therein and a, two piece dieconstruction.

Fig. 5A is a section on the line 5A--5A of Fig. 2 illustrating the twopiece die construction and the burr clearance relief for permitting thepassage of a burr through the die when feeding the workpiece.

Fig. 6 is a section on the line 6-6 of Fig. 2, which illustrates thekeyways in the holder and the slidable pin for keying the punch to theholder and retaining the punch on the guide.

Fig. 7A illustrates in section, the action of this punch on its initialnibbling stroke.

Fig. 7B indicates the slug which is removed on this stroke.

Fig. 7C is a view taken after several nibbling operations have takenplace, indicating the pileup of the slugs, and showing how they dropoff, one by one, to pass by the keyed section of the punch.

Fig. 8 is a view illustrating the nibbling device and method of usewhich will permit cutting out a square blank and showing the nibblingpunch about to punch out a circular segment after which it will turn acorner to start another leg of the square work-piece.

Fig. 9 is a view illustrating the punch around the corner and showingthe square blank cut thereby.

Fig. 10 is a partial fragmentary view illustrating my device cutting anoutside convex contour and starting said contour inside a sheet from ahole perforated therein.

Fig. 11 illustrates a similar view but with a punch-cutting sectionhaving a convex instead of a straight periphery so as to provide anessentially finished edge on the inside concave contour of thiswork-piece.

Fig. 12 illustrates how our punches and dies can be applied to astandard nibbling device, such as is widely used now throughoutindustry.

Fig. 13 indicates in side sectional elevation, a modified punch and itscompanion die in which the underhung key is eliminated.

Fig. 14 is a section taken as noted on the line l4l4 of Fig. 13 whichillustrates how the keyway is formed inwardly from the half-round diesection to engage a key formed in the round punch section.

Fig. 15 illustrates still another modification of our apparatus andmethods in which special keying of the punch or die is eliminated bypositioning the punch and its companion die aperture considerably offcenter, so that the workstop becomes the key and the punch and diefunction in a castering manner, which permits the method of working to ascribed line.

Fig. 16 is a section of the die and its anti-friction turntable in whichit is mounted, taken as noted on the line l6l 6 of Fig. 15.

Fig. 17 is a section, taken as noted on the line I'II'l of Fig. 15, andillustrating the shaped stripping guide for stripping light metalwithout drawing the metal up in the guide.

In the following description we discuss our novel half -round nibblingpunch and die which can be used for three different methods of nibblinThat is, nibbling to a. contoured template, nib;- bling a work-piecemounted to turn on used ten.- ters, or slide parallel. to a gauge stop,or to a scribed line formed on. the work-piece itself.

In the illustrations we indicate four different methods of maintainingvthe shaped punch and die in alignment. We illustratethis novel. nibblingpunch and die keyed as is now the practice and by three new novel:methods heretofore not utilized for this purpose. While we are concernedprimarily with the novelty of our shaped nibbling punch and die and themethods of use, the combination with the three alternate meth: ods shownfor keying the punch to the die; along with the novel stripping means,are deemed of great importance in the satisfactory operations of ourinvention for all the required nibbling conditions.

' The two existing methods of keying a punch in aligned relationship toa die which we illustr'ate herein, are only illustrated to indicate theadaptability of our shaped punch tov the existing nibbling processes andapparatus now utilized by industry.

In Figs. 1 and 2 we illustrate the preferred form of our companionnibbling punch and die as used in the self-contained punching unitsimilar in function to that shown in Patent No. 1,955; 866 assigned toour interests. When used in a nib: bling machine, this unit would takethe form illustrated herein, which is identical to that of holder 55-56illustrated in Patent No. 64,011 also assigned to our interests. It willbe obvious that the die in can be forced out of the bottom 22 of holder20 and the punch assembly 30 can be lifted out of the top 2| of holder26 to effect rapid replacement of punch and die, as is shown in Fig. 15of the above patent.

Having thus established the background for this device, we will alsorefer to Fig. 3 and con-. sider'the features of the preferred version ofour device representing the improvements over. the prior art. Punchassembly 3!] comprises the punch 32 having the threaded head extremity33, and the punch-cutting extremity 3,5, which with co-operating dieopening 51 of die 5.0, elfects the removal of. metal from work-piece 60.It will be noted that co-operating cutting surfaces 35 and of punch 32and die 5.0 respectively, are arcuate and effect a semi-circular cut.This shape and slight modifications of it is the main feature of ourinvention, as it provides the versatility and ease of manufacture of theround nibbling punch and die with the finished edge ofthe rectangularpunch and die mentioned heretofore. This construction also reduces thestripping force required over the comparative round nibbling punch.In'addition, this shape makes possible any contoured configuration ofwork piece with a finished edge. The reasons for this versatility innibbling and ease of manufacture as a result of this shapedconstruction, will be discussed hereinafter;

Extending downwardly from the punch cutting edge 35. is the work-piecestop, 35. Extending under. cutting. edge 35 from this stop 35 is theunique key 3'!- which serves. to key the shaped die assembly. 50. to thepunch assembly 33, as illustrated in Fig. 5. It will be obvious that thekey 31 bearsv against the. fiat surface 52 of die 50, so that onearcuate cutting surface 35 of punch assembly 30 will always be in linewith a cornplementary semi-circular. die opening 5|; of the dieassemblyill, so that .in eifect they are keyed together for relativealigned slidable movements...

such as occurs when the punch assembly 30 moves toward die assembly inthe perforating opera: tion while being held against relative angular,or rotative movements. As shown, punch 32 0f ass sembly 30 is arelatively simple shape yet includes the key 31 formed out of the punchitself. Con: versely, referring also to Figs. 5 and 5A, i is obviousthat single piece die 50 would require complicated internal machining.To eliminate this expensive machining we utilize a simple round die 54having a cutting edge 5i formed therein and an accurately made clearancecoun: terbore 53. In this round die 54, and counterbore 53! we insertthe semiecircular stepped plug which is also a simple turned part. Itwill now be apparent that plug 55 can be soldered or brazed to die 54 asillustrated in these views. 01" can be left as a loose piece in die 54since the key 31 will always keep it in alignment and it will be,supported by the bed of the press 25 for nibbling.- It will be obviousthat when punch 32 turns with a loose, freely movable plug 55 it needonly turnthe plug 55 in following a contour, rather than the whole dieassembly 51 in the method described hereinafter. This loose constructionalso in; creases die life as the entire round cutting edge 51 can beutilized giving twice the life of a onepiece die. This construction alsomakes possible the perforating of a round starting hole using aroundpunch since only the plug and nibble punch must be removed to permitperforating a round hole from a round punch.

It is well to point out here that the above loose construction is onlysuited to nibbling the harder alloys since the burr clearance recess 56of die assembly 5| is not then required as there is no tendency to draga burr down into. the die when nibbling hard materials. However, we haveil-, lustrated in these figures the construction suited to both soft andhard materials in which the die assembly 50 must be provided with theburr clearance recess 56 shown best in Figures 2 and 5A. In thisconstruction stepped plug 5.5 is brazed or otherwise fastened to rounddie 54 and then the burr clearance 55 is ground in the die assembly atso that a downwardly formed burr in soft material will clear the dieassembly 5|; by means of recess 55 when the Work-piece is fed towardwork stop 35 of punch 32 lhis has proven valuable as otherwise the burrcustomarily found in perforating soft materials projects into the dieassembly 5%] and will not permit feeding the work-piece.

since clearance must be provided in punching equal to roughly 10% of themetal thickness be ing punched, it is obvious that clearance can bemachined more easily and economically in punch body 32 from the. cuttingedge 35 upwardly for the length of surface 3, Clearance is thus pro:vided in the punch rather than in the dieas is the customary practice.For punching various thick: nesses, punches having various clearanceswould be employed rather than dies having variable clearances. This isadvantageous also, since one die. will outwear three or more punches andextra dies. are not required, as is the standard practice.

Referring back to Fig. 1-, it will be observed that the self-containedholder unit 20 is of a standard size, and that in this instance someclearance is apparent between ram 25 and nut M of punch assembly 38, asthe press stroke is greater than the perforating stroke of the unit.With a longer stroke press, this clearance would be Sllbisfil}? tial. Asdiscussed; previously, an extreme clear-e 7 ance condition is nottroublesome in single hole perforating work, but in nibbling it createsdifllcuity. In the nibbling operation the punch is operatingcontinuously at from 165 to 800 perforations per minute, so that punchesand dies dull rapidly and stripping becomes difiicult within a shortwhile. In our usual self-contained perforating unit, the strippingspring is always under preload, either because the stripping springs arecontained under compression or are preloaded by compressing the springfrom the action of the press ram prior to any contact of the punch withthe work-piece. This creates difficulty however, if the punch sticks inthe work-piece due to the poor stripping, as when it releases from themetal in a delayed action, it has considerable stored energy in themoving punch and the heavy spring. Since the spring itself is stillunder load at the movement of exit from the work-piece, this storedenergy causes the punch to spring up in many cases out of its socket,and it must be replaced manually. Considering, that one nibbling punchmay make one thousand or even more perforations on one piece whereas aperforating punch may make only a few perforations, it will be obviousthat poor stripping due to dull punches and dies is a serious problem toconsider in nibbling. Since in some machines, a preloaded spring cancause the punch to leap clear of the holder, so that it will not bealigned for the next stroke, this must be avoided in the continuousnibbling operation, as it would be dangerous for the ram to come downwith the punch clear of the holder. Obviously, this is not critical insingle stroke operation, as the punch can be replaced manually prior tothe next perforating operation, but in nibbling the ram is operatingcontinuously. To overcome this difliculty and prevent damage to key 31of our punch 32, we employ oppositely wound nested springs matched tothe nibbling punch, so that the stripping loads required for nibblingany material thickness is balanced completely throughout the travel ofthe punch by the force of the nested compressed stripping springs 51 and58 for a dull punch 32 and die'50. In addition, the length of theheavier stripping spring 58 is such that it is under no load at theinstant the punch 32 withdraws from the work-piece 60. The resilientforce required to overcome any minute variations in stripping pressureat zero or thin metal thicknesses is provided entirely by light spring51. It is now apparent that by utilizing only the light spring 51, afterthe punch 32 withdraws from the metal, the dynamic force applied againstpunch 32 is much less, reducing or eliminating the tendency of the punchto bounce. To maintain this condition, we provide the adjustable nuts404| for keeping the same relation between punch cutting surface 35 andstripper 42 and springs 51 and 58. If required, spacers can be insertedbetween nuts 40 and 4| which will accommodate any variations between thelength of the springs 51 and 58, so that they can be properly matched toprovide the desired stripping condition. The reduction or elimination ofthe bounce of punch 32 is extremely important in the device of Figs. 1through 11 as if the operator is feeding when the punch 32 bounces, thekey 31 may be damaged due to the blow thereon.

As shown in Figs. 2 and 6, another important feature of our inventionresides in the method of keying the punch and die in relation to theholder. The usual practice for keying the punch is to key the guide tothe holder by a key and the punch to the guide by means of acomplementing guide shape which guides the shaped tip of the punch. Inour present invention we utilize a key pin on the punch which extendsthrough the guide to engage the key ways in the holder. This eliminatesa build-up in tolerance as only the tolerance between one key and keywayis involved. With this construction the guide bore can be round ratherthan shaped to the punch' end. We go a step farther in this novel keyingdevice for our nibble punch and die and'utilize an extensible key pin 46which can be extended to engage the holder so as to guide the punchassembly 30 and die assembly 50 in aligned fixed relationship withkeyways 21 or 28 in holder or retracted so that only the punch assembly30 and die assembly are maintained in aligned relationship. The key pin46 is extended in the event a gauge is used for nibbling to a straightline or for nibbling a circle from a fixed center normal to the tangentcut provided by the flat face 34 of punch 32. To key the punch assembly30 to the holder apparatus 20, we provide a pin 46 with a resilientsplit 41 which can be extended out of bore 39 of punch 32 and slot 43 ofstripper guide 42 by pushing on the pin 46 through bore 59 of guide 42.With pin 46 extended it will be possible to engage either key way slot21 or 28 of holder arm 2| to maintain punch assembly 30 and its keyeddie 50 in selective fixed positions. Pin 46, when retracted, is withinslot 43 of guide 42 so that only punch 32, guide 43 and die 50 are keyedfor aligned movement together, but they are freely revolvable as analigned unit in holder 20 to follow a template 10. This is the method ofnibbling shown in Fig. 1 and Figs. '1 through 11.

The freely revolvable punch and die provides an important advantage asit permits the nibbling of longer work-pieces than is possible on aconventional nibbler. For instance, when nibbling a hole inside a largerectangular sheet, the work-piece can be fed in any direction. Thispermits the use of a machine having a shorter throat depth since theshortest distance to the edge of the work-piece can always be within thethroat area of the machine.

Having discussed how our punch assembly 30 and die 50 can rotate freelyfor following a template 10, or be keyed to holder 20 for holding a lineparallel to a gauge bar, or a circle from a pivotal center normal to theflat cutting face 34 of punch 32, we will now refer to Figs. 1 and 7Athrough 70 to show the template operation in detail. It will be observedin Fig. 1 that template I0 is bearing against the step 44 in strippingguide 42 and that because of key 46 and guide 42, punch 32 is cuttingwork-piece on a line governed by the template 10. It will be noted alsothat template 10 could also bear against the flat face 34 of punch 32,but we have found its action is better if it bears against the step 44of guide 42 to control the punch. We will now refer to Figs. 7A through'70 for the detailed operation.

It will be noted in Fig. 7A that work-piece 60 is resting against stop36 of punch 32 and that template I0 is against stripping guide 42. Fig.7B illustrates that the punch 32 has descended, causing slug 6| to besheared out of work-piece 60. Fig. illustrates the next nibbling strokeafter which slug 6| drops out of die opening 5| and is deflected off theslanted face 38 of key 31 into die clearance space 53. Once clear, itwill go down the slug chute of the machine.

Fig; 8 illustrates nibbling around a square template 10 and shows thepunch 32 about to cut the slug 66 out of work-piece 60, after whichpunch 32 will be manually turned in its own perforation, which it hasjust made and continue around the corner as is illustrated in Fig. 9.This is the outstanding feature of our invention in that it provides afinished edge 15 and yet can go around a square corner while operating,without damaging the punch .or die. This finished edge means thatcurpunch can be larger, operating .at a much slower speed than isconventionally used in from inside a sheet by using a perforation 69 inwork-piece :60 and removing punch assembly 30 and re-inserting throughperforation 69. This is another outstanding feature of our inventionsince the stop 35 would preclude this rapidity of operation if the punch32 was attached tot-he ram "25' as is done on conventional nibblers.

Fig. 11 illustrates nibbling an inside contour 13 in which punch 32 anddie 50 would have a convex face 14 instead of the fiat face 34. Convexsurface I4 can also be used for outside contours but does not give quiteas god a finished edge as fiat face 34. Combinations of flats and radiion this finished cutting edge could provide almost any condition desiredfor a particular class of work-piece. I I e In Fig. 12 we illustrate theapplication of the half-roundnibbling punch and dieto aconventiona'lnibbler. In this'configuration e illustrate the old expedient ofmaintaining a shaped punch and die in aligned relationship by means of arigid'attachment after alignment. Keys are also sometimes employed forthis purpose in conventional machines, or inself-containedholderssuch asin Fig'. 1. We show a nibbling punch 82 having a half-round punchsection at terminating in 2 cutting edge -85 and work-stop 86 and acomnames are so. Punch a: is rigidly attached to the keyed ram H or aconventional nibbler frame 83; so that it cannot revolve. D ie.80 isrigidly attached to bed 81 of nibble r frame 83 so that it is maintainedaligned relatio'nship" with punch '82. In" this configuration only thework stop 36 is required as both the punch 82 and die 80 are maintainedin alignment. A positive stripper 8'8 mounted'on-nibbler frame .83 hasan opening Ii}! through which pun-ch 82 projects. In this airangementthe' template in and work-piece 60, of ourpreviousillustrations, is caused to'move in the plane of the table tochange the contour rather than turningthe pun-ch as. previouslydiscussed.

t wu e obvious to one skilled in the art that this old expedient ofkeying a shaped punch and die can be equauy applied .to the holder 20'or rig; 1 and that with the extending key 31 removed, theconfiguration-would be identical to Fig. 12 but in a self-containedunit.

Referring now to Figs. 13 and 14 we show our Second .alternateno'velkeying means. In this arrangement punching assembly 90 is identical topunchassembly of Fig.1, except that punch 92 has .a key 9'1v formedtherein whichis engagedby keyway I02 formed within the half round diesection IIJI of die I00. It will be noted that the key and keyway areformed inwardlybecause an outwardly extending key on the punchflZ,projecting above the .die I00, would prevent the action of Figs; 8 and9. The construction illustrated here is more satisfactory when nibblingheavier stock and following a template as there is no key obstructionunder the cut-tingedgefili of punch 92,. However, .it will be obvioustoone skilledin the art that .die section I01I with its key I02 is muchmore difli-cult to fabricate than the die of Fig; .1. I

Referring now to Figs. 15, 16 and 17, we illustrate our arrangementwhich provides a novel and more simple key means which makes possible amethod of following a scribed line with our shaped nibbling punch, sothat a template or key is unnecessary. l We illustrate a self-containedholder I20 which is enlarged in plan. form so ;that it will accommodatethe anti-friction turntables E and I55 assembly I30 identical inconfiguration to punch assembly 30 of Fig. 1; but embodying .a diiferentpunch I32 having adownwardly extending stop I36 engaging a die I50. .Asis illustrated in Fig. 17, stop I36 is merely the partial section of thehalf-round end T34 of the punch I32. remaining when cutting. edge 2351sformed. This extends downwardly into die I as is illustrated in Fig. 16and serves to key the punch I32 to the die I50 whichis removablykeyedsby key I51 to turntable I Since-the keyed punch assembly I30 is toall intentsand purposes a part of turntable Hi5v with respect tomovement about axis I and.keyed die I50 is apart .of turntable I55, stopI36 acts within die I50 as a remote key so that they must move in unisonabout axis I60. Obviously guide IE2 and turntable I45 could be made inone piece as could be die I50 and turntable I55 without affecting theoperation. Because of this remote location of the axisof punching fromthe axis of rotation I60, the feeding of a workpiece against stop I36causes punch I32 and die I50 to caster in unison about axis I60, thusassuring the nibbling punch following the direction of feed by theoperator. In this arrangement the nibbling can be made to followascrib'edline. Because no template is required in this configuration ofour device, the guide I42 has a shaped end I43 conforming to the shapeI34 of punch I32. This assures stripping light gauge material.

Having thus describedour invention, we claim:

. 1. In a nibbling apparatus, a freely rotatable diehaving cuttingedges, and a punch having a working end which in cross section is ofgenerally circular segmental shape and which has meeting circumferentialand chordal cutting edges, said die having complementary cutting edges,said punch'being extended axially at one side beyond said working end todefine a work stop. section and a key, said key cooperating with saiddie to permit relative axial movement of said punch with respect to-saiddie ane preventing relative angular movement between said punch andd'ie. V Y,

2. In nibbling apparatus, a freely rotatable die having cutting edges,one --of which is atthe 1 1 end of a fiat face, and a punch having aworking end which in cross section is of generally circular segmentalshape, the meeting circumferential and chordal edges of one side of saidend providing cutting edges which are complementary to and whichcooperate with the cutting edges of said die, and said punch beingextended axially at one side to define a work stop section and a key,said key having a fiat face which engages said first mentioned flat faceto permit relative axial movement of said punch with respect to said diewhile preventing relative angular movement between said punch and die.

3. In nibbling apparatus, a freely rotatable die having cutting edges,and a punch having a working end which in cross section is ofgeneralwhich cooperates with said die to permit relative axial movementof said punch with said die while preventing relative angular movementbetween said punch and die.

4. In nibbling apparatus, a freely rotatable .die, a freely rotatableguide sleeve, a punch reciprocable in said sleeve, and means keying saidpunch to said sleeve so that relative angular movement between them isprevented, said punch and die having cooperating cutting edges and saidpunch having an extension for keying said die to it so that the punch,sleeve and die may turn only as a unit and so that said punch mayreciprocate with respect to the die, the lower end of said sleeve beingformed to provide diametrically opposed shoulders for engaging atemplate to control the turning movements of said punch and die so thatin cutting a Workpiece a finished edge will be produced.

5. In combination, a nibbling punch and die,

said punch having a cutting shank portion which is generallysemi-cylindrical in shape and which has a cutting end face intersectingsaid shank portion and defining with said shank portion acircumferential and a generally chordal cutting edge, said punch havingan extension axially beyond said end face which has a side face that isa continuation of said chordal cutting edge, said die being generallycylindrical in shape, and a plug positioned in and fitting said die,said plug being generally semi-cylindrical in shape and having agenerally chordal side complementary in shape to the said side face ofsaid punch extension.

6. A nibbling punch having a working portion which has an outsidesurface that is arcuate in profile, an inside surface which is connectedat opposite lateral ends thereof to said arcuate surface, an end faceintersecting said inside and said outside surfaces and defining withsaid surfaces cutting edges, and an extension projecting axially beyondsaid end face, said extension having one side surface thereof which is acontinuation of said inside surface and being connected by a narrow neckportion with said end face, and terminating in an end portion whichprojects laterally at both sides of the axis of said punch, said neckportion having an area less than half the area of said end face.

'7. A nibbling punch having a working portion which has an outsidesurface that is arcuate in profile, an inside surface which is plane andwhich extends between the ends of said outside surface and in adirection axial of said outside surface, an end face intersecting saidinside and said outside surfaces and defining with said surfaces cuttingedges, and an extension projecting axially beyond said end face, saidextension having one side surface which is plane and which lies in thesame plane as said inside surface, and said extension being connected bya narrow neck portion with said end face and terminating in an endportion which projects laterally at both sides of the axis of saidpunch, said neck portion having an area less than half the area of saidend face.

8. In nibbling apparatus, a rotatably mounted punch having an outsidesurface that is arcuate in profile, an inside surface which is connectedat opposite ends to said arcuate surface, an end face intersecting saidinside and said outside surfaces and defining with said surfaces cuttingedges, and an extension projecting axially beyond said end face, saidextension being of less area than said end face and having one sidesurface thereof which is a continuation of said inside surface, and adie mounted to be freely rotatable about an axis extending in the samedirection as the axis of rotation of said punch, said die having acutting edge complementary to the cutting edge of said punch, one partof the cutting edge of said die being engaged by the said one sidesurface of said extension to key the punch and die to rotate together.

9. In nibbling apparatus, a rotatable punch having an outside surfacethat is arcuate in profile, an inside surface which is plane and whichextends between the ends of said outside surface, an end faceintersecting said inside and said outside surfaces and defining withsaid surfaces cutting edges, and an extension projecting axially beyondsaid one face, said extension being of less area than said end face andhaving one side surface which is plane and which is a continuation ofsaid inside surface, and a die mounted to be freely rotatable about anaxis extending in the same direction as the axis of ro tation of saidpunch, said die having a bore which is semi-cylindrical in cross-sectionand having a cutting edge complementary to the cutting edge of saidpunch, said bore having onebounding face which is plane and which isengaged by the plane face of said extension to key said punch and dietogether.

10. In combination, a nibbling punch and die, said punch beingreciprocable axially and having a cutting shank portion which isgenerally semi-cylindrical in shape and which has a cutting end faceintersecting said shank portion and defining with said shank portion anarcuate and a chordal cutting edge, said punch having an extensionprojecting axially beyond said end face which has a plane side facecoplanar with said chordal cutting edge and extending in the directionof the punch axis, said extension being connected by a narrow neckportion with said end face and terminating in an end portion whichprojects laterally at both sides of the axis of said punch, said neckportion being of less than half the area of said end face, said diebeing freely rotatable about an axis coaxial with said punch and havingcutting edges complementary to those of said punch and having a planechordal surface against which the plane side face of said extensionbears as the punch reciprocates.

11. In combination, a support, a sleeve slidaizle axially in saidsupport, a nibbling punch and die, said punch being reciprocable axiallyin said sleeve, means for selectively keying said punch to said sleeveor said punch and sleeve to said support, said punch having a shankportion and a cutting end face which intersects said shank portion andwhich defines with said shank portion the cutting edges of said punch,said punch having an extension axially beyond said end face which has aninside plane face that extends in the direction of the axis of thepunch, said extension being connected by a narrow neck portion with saidend face and terminating in an end portion which projects laterally atboth sides of the axis of said punch, said neck portion being of lessthan half the area of said end face, said die being freely rotatable andhaving cutting edges complementary to those of said punch and having aplane chordal surface against which the inside plane surface of saidextension bears as said punch reciprocates.

12. In combination, a nibbling punch and die, said punch having a shankportion and a cutting face which intersects said shank portion and whichdefines with said shank portion the cutting edges of said punch, saidpunch having an extension projecting axially beyond said end face whichhas an inside plane surface that extends in the direction of the axis ofthe punch, said extension being connected by anarrow neck portion withsaid end face and terminating in an end portion which projects laterallyat both sides of the axis of said punch, said neck portion being of lessthan half the area of said end face, said die being freely rotatable andhaving cutting edges complementary to those of said punch and having aplane chordal surface against which the inside plane surface of saidextension bears as said punch reciprocates.

13. A nibbling punch having a. shank portion and a cutting face whichintersects said shank portion and which defines with said shank portionthe cutting edges of said punch, said punch having an extensionprojecting axially beyond said end face which has an inside planesurface that extends in the direction of the axis of the punch, saidextension being connected by a narrow neck portion with said end faceand terminating in an end portion which projects laterally at both sidesof the axis of said punch, and said neck portion having an area lessthan half that of said end face.

GEORGE F. WALES. PAUL H. TAYLOR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 363,917 Snyder May 31, 1887 1,802,502 Doyle Apr. 28, 19311,831,374.- Topping Nov. 10, 1931 1,977,795 Gray Oct. 23, 1934 2,035,448Andersson Mai: 31, 1936 2,182,544 Murrian et a1. Dec. 5, 1939 2,225,342Hyatt Dec. 17, 1940 2,309,358 Robinson Jan. 26, 1943 2,468,998 ParsonsMay 3, 1949

